One of the things you learn in eastern style form of meditation is that "you" (the canvas-experience consciousness) are neither the source of your senses (obviously), nor of your ideas, nor of your emotions. All three are simply things that happen to "you". Even your ideas of "I" are generated and you experience them.
And yet the fact that the canvas-experience consciousness exists is the most irrefutable thing there is, because there IS experience. Is it a dream? Is it a simulation? Well, whatever it is, IT IS.
And just as that is obvious and irrefutable, it also seems pretty much impossible to show that anything other than yourself has this canvas-experience consciousness. As you say, you cannot know that behind my eyes there is this also.
Edit: Intelligence is also orthogonal to consciousness entirely. As I said your consciousness is not the generator of intelligent thoughts, so it is perfectly possible that intelligent thoughts can be generated by not-conscious systems, and for conscious systems to be not-intelligent.